Reuse the nonexistent handler frontend for transition handlers

src/stub-cache.cc

Index: src/stub-cache.cc
diff --git a/src/stub-cache.cc b/src/stub-cache.cc
index edb60257daf38cab3722111dfa8467776ef9fd98..a58dc9887bd8878076c6fc3955fe376b9be044b6 100644
--- a/src/stub-cache.cc
+++ b/src/stub-cache.cc
@@ -803,7 +803,9 @@ Register PropertyHandlerCompiler::Frontend(Register object_reg,
 }
 
 
-void NamedLoadHandlerCompiler::NonexistentFrontend(Handle<Name> name) {
+void PropertyHandlerCompiler::NonexistentFrontend(Handle<Name> name,
+                                                  Register scratch1,
+                                                  Register scratch2) {
   Label miss;
 
   Register holder_reg;
@@ -819,26 +821,24 @@ void NamedLoadHandlerCompiler::NonexistentFrontend(Handle<Name> name) {
     last_map = handle(holder()->map());
   }
 
-  if (last_map->is_dictionary_map() && !last_map->IsJSGlobalObjectMap()) {
-    if (!name->IsUniqueName()) {
-      ASSERT(name->IsString());
-      name = factory()->InternalizeString(Handle<String>::cast(name));
+  if (last_map->is_dictionary_map()) {
+    if (last_map->IsJSGlobalObjectMap()) {
+      Handle<JSGlobalObject> global =
+          holder().is_null()
+              ? Handle<JSGlobalObject>::cast(type()->AsConstant()->Value())
+              : Handle<JSGlobalObject>::cast(holder());
+      GenerateCheckPropertyCell(masm(), global, name, scratch1, &miss);
+    } else {
+      if (!name->IsUniqueName()) {
+        ASSERT(name->IsString());
+        name = factory()->InternalizeString(Handle<String>::cast(name));
+      }
+      ASSERT(holder().is_null() ||
+             holder()->property_dictionary()->FindEntry(name) ==
+                 NameDictionary::kNotFound);
+      GenerateDictionaryNegativeLookup(masm(), &miss, holder_reg, name,
+                                       scratch1, scratch2);
     }
-    ASSERT(holder().is_null() ||
-           holder()->property_dictionary()->FindEntry(name) ==
-               NameDictionary::kNotFound);
-    GenerateDictionaryNegativeLookup(masm(), &miss, holder_reg, name,
-                                     scratch2(), scratch3());
-  }
-
-  // If the last object in the prototype chain is a global object,
-  // check that the global property cell is empty.
-  if (last_map->IsJSGlobalObjectMap()) {
-    Handle<JSGlobalObject> global =
-        holder().is_null()
-            ? Handle<JSGlobalObject>::cast(type()->AsConstant()->Value())
-            : Handle<JSGlobalObject>::cast(holder());
-    GenerateCheckPropertyCell(masm(), global, name, scratch2(), &miss);
   }
 
   FrontendFooter(name, &miss);
@@ -861,6 +861,14 @@ Handle<Code> NamedLoadHandlerCompiler::CompileLoadConstant(
 }
 
 
+Handle<Code> NamedLoadHandlerCompiler::CompileLoadNonexistent(
+    Handle<Name> name) {
+  NonexistentFrontend(name, scratch2(), scratch3());
+  GenerateLoadConstant(isolate()->factory()->undefined_value());
+  return GetCode(kind(), Code::FAST, name);
+}
+
+
 Handle<Code> NamedLoadHandlerCompiler::CompileLoadCallback(
     Handle<Name> name, Handle<ExecutableAccessorInfo> callback) {
   Register reg = CallbackFrontend(receiver(), name, callback);
@@ -970,15 +978,10 @@ Handle<Code> NamedStoreHandlerCompiler::CompileStoreTransition(
       iter.Advance();
     }
     if (!last.is_null()) set_holder(last);
-  }
-
-  Register holder_reg = FrontendHeader(receiver(), name, &miss);
-
-  // If no property was found, and the holder (the last object in the
-  // prototype chain) is in slow mode, we need to do a negative lookup on the
-  // holder.
-  if (is_nonexistent) {
-    GenerateNegativeHolderLookup(holder_reg, name, &miss);
+    NonexistentFrontend(name, scratch1(), scratch2());

[Igor Sheludko, 2014/08/04 10:27:58]

Now this thing will generate a frontend footer with a miss case...

+  } else {
+    Frontend(receiver(), name);

[Igor Sheludko, 2014/08/04 10:27:58]

... (same here) ...

+    ASSERT(holder()->HasFastProperties());
   }
 
   GenerateStoreTransition(transition, name, receiver(), this->name(), value(),